NASA Announces New Mars Landing SitesCovering Twice The GroundIf NASA has its way, not one, but two rovers will soon be roaming the Red Planet, investigating areas that might have once held bodies of water.

NASA managers announced the two landing sites for the Mars Exploration Rovers (MERs) Friday, saying both sites were scientifically compelling. Four prospects were under consideration and NASA made its final decision based not only on scientific allure, but spacecraft technical concerns, said space science program chief Ed Weiler.

"In choosing where to go, we need to balance science value with engineering safety considerations," said Weiler. The first rover, scheduled for launch on May 30, will be directed to Gusev Crater, located 15 degrees south of Mars' equator (see map, bottom). The second robotic scout, slated for liftoff on June 25, is targeted to land at Meridiani Planum, which features rich deposits of gray hematite, an iron oxide mineral associated with water. Meridiani Planum is about 2 degrees south of the equator and halfway around the planet from Gusev Crater.

Doing The Job Before The Lights Go OutThe first rover should reach its landing site on Jan. 4 and the second on Jan. 25. Each is expected to last for about three months before dust blankets the rovers' solar arrays, cutting off their power. The rovers' masts will carry remote sensing instruments, including high-resolution color cameras and infrared spectrometers for studying the minerals in rocks and soil. The rovers also will be equipped with a microscopic imager to see micron-size particles and textures, an alpha-particle/x-ray spectrometer to determine what elements the samples contain, and a Moessbauer spectrometer for determining the mineralogy of iron-bearing rocks.

Each rover will carry a rock abrasion tool, similar to a geologist's rock hammer, to remove weathered surfaces from rocks and expose their interiors for analysis. The overall scientific focus of the mission is to investigate what role water played on Mars and to determine how suitable the conditions would have been for life, said Cornell University's Steve Squyres, a principal investigator.